Peripheral and bimanual reaching in a stroke survivor with left visual neglect and extinction

Whether attentional deficits are accompanied by visuomotor impairments following posterior parietal lesions has been debated for quite some time. This single-case study investigated reaching in a stroke survivor (E.B.) with left visual neglect and visual extinction following right temporo-parietal-frontal strokes. Unlike most neglect patients, E.B. did not present left hemiparesis, homonymous hemianopia nor showed evidence of motor neglect or extinction allowing us to examine, for the first time, if lateralised attentional deficits co-occur with deficits in peripheral and bimanual reaching. First, we found a classic optic ataxia field effect: E.B.'s accuracy was impaired when reaching to peripheral targets in her neglected left visual field (regardless of the hand used). Second, we found a larger bimanual cost for movement time in E.B. than controls when both hands reached to incongruent locations. E.B.'s visuomotor profile is similar the one of patients with optic ataxia showing that attentional deficits are accompanied by visuomotor deficits in the affected field.

Pictorial depth cues always influence reaching distance

We report five experiments to test the influence of pictorial depth on reaching. Our core method is to project a wide-field background of linear perspective and/or texture gradient onto a tabletop, and to measure the amplitude of reaches made to targets within it. In 63 healthy participants performing immediate open-loop reaches across Experiments 1-4, we observed a clear effect of pictorial depth. This effect was driven specifically by the convergence of the background pattern at the target position: for each additional degree of pictorial convergence, reaching distance increased by half a millimetre. In the individual experiments, we applied manipulations that might be expected to modify the influence of pictorial depth. We found no evidence that the effect was modified with monocular viewing, or when participants responded with the left hand, or if a memory delay was inserted before the response. Nor did participants become less susceptible to pictorial depth when visual feedback of terminal reaching errors was provided, although visual feedback during the reach did mitigate the influence of pictorial depth. Finally, the visual form agnosic patient DF showed an entirely normal effect of pictorial depth cues, which leads us to question the idea that this effect emanates from visual analyses of size and shape in the ventral stream, rather than from the dorsal stream, or from earlier stages of visual processing.

No short-term treatment effect of prism adaptation for spatial neglect: An inclusive meta-analysis

Despite 25 years of research on the topic, there is still no consensus on whether prism adaptation is an effective therapy for visuospatial neglect. We have addressed this question through a meta-analysis of the most well-controlled studies on the topic. Our main meta-analytic model included studies with a placebo/sham/treatment-as-usual control group from which data from right hemisphere stroke patients and left-sided neglect could be aggregated. The short-term treatment effects on the two commonly used standard tests for neglect, the conventional Behavioural Inattention Test (BIT-C) and cancellation test scores were combined into one random effect model justified by the fact that 89% of the BIT-C score is determined by cancellation tasks. With this approach, we were able to obtain a larger and more homogeneous dataset than previous meta-analyses: sixteen studies including 430 patients. No evidence for beneficial effects of prism adaptation was found. The secondary meta-analysis including data from the Catherine Bergego Scale, a functional measure of activities of daily living, also found no evidence for the therapeutic effects of prism adaptation, although half as many studies were available for this analysis. The results were consistent after the removal of influential outliers, after studies with high risk-of-bias were excluded, and when an alternative measure of effect size was considered. These results do not support the routine use of prism adaptation as a therapy for spatial neglect.

Skill and self-knowledge: empirical refutation of the dual-burden account of the Dunning-Kruger effect

For many intellectual tasks, the people with the least skill overestimate themselves the most, a pattern popularly known as the Dunning-Kruger effect (DKE). The dominant account of this effect depends on the idea that assessing the quality of one's performance (metacognition) requires the same mental resources as task performance itself (cognition). Unskilled people are said to suffer a dual burden: they lack the cognitive resources to perform well, and this deprives them of metacognitive insight into their failings. In this Registered Report, we applied recently developed methods for the measurement of metacognition to a matrix reasoning task, to test the dual-burden account. Metacognitive sensitivity (information exploited by metacognition) tracked performance closely, so less information was exploited by the metacognitive judgements of poor performers; but metacognitive efficiency (quality of metacognitive processing itself) was unrelated to performance. Metacognitive bias (overall tendency towards high or low confidence) was positively associated with performance, so poor performers were appropriately less confident-not more confident-than good performers. Crucially, these metacognitive factors did not cause the DKE pattern, which was driven overwhelmingly by performance scores. These results refute the dual-burden account and suggest that the classic DKE is a statistical regression artefact that tells us nothing much about metacognition.

Righteous Adam, Sinister Eve

The symbolism of laterality in images implies that the virtuous figure is represented on the right of the scene whereas the sinful character is depicted on the left. In portraits of male and female characters this has reflected and reinforced stereotypes and inequalities down the ages. Given these premises, we hypothesized that the prototypical representations of Adam and Eve, as a man and a woman conflated with notions of virtue and vice, would show a non-random arrangement. We tested this hypothesis, sampling artistic depictions of the Garden of Eden, from the twelth century to the present day in three separately-collected series of 100, 99, and 142 images respectively. Eve is depicted to Adam's left significantly more often than chance (between 70% and 83%), particularly in pre-1600 artworks. We interpret this asymmetry as reflecting the perceived lesser status of women in relation to men, since the allegorical incipit of humankind. We also provide experimental evidence that this asymmetry, although pervasive, has not been internalized by modern viewers. Cognitive sciences account for this spatial asymmetry in terms of preference for figures placed within the left visual field of the observer, i.e., within the right space of the objective scene.

On line bisection: Validity and reliability of online measures of pseudoneglect

This study assessed pseudoneglect using line bisection and perceptual landmark tasks in two matched online sessions. Line bisection bias was characterized by the traditional measure of Directional Bisection Error (DBE), and by Endpoint Weightings Bias (EWB), derived from an "endpoint weightings" analysis, made possible by the independent manipulation of left and right endpoints. EWB is proposed to index the relative attentional allocation to the two ends of the line. The expected leftward bias (pseudoneglect) was found, with larger effect sizes for EWB (d = -0.34 in both sessions) than for DBE (-0.22 in Session 1 and -0.14 in Session 2). Although EWB was slightly less reliable than DBE, it was more sensitive to pseudoneglect, and the endpoint weightings method has further advantages, including the option of an additional measure of non-lateralized attention. A substantial proportion of participants had difficulty following the instructions for the landmark task, which highlights the need for clear instructions and performance checks for this task. This study shows that line bisection can be used to measure pseudoneglect online, and provides grounds to suggest that the task should routinely include the independent manipulation of left and right endpoints, so that an endpoint weightings analysis can be performed.

Endpoints and viewpoints on spatial neglect

In this issue of the Journal of Neuropsychology, Abe and Ishiai (2022) report an experiment designed to probe the subjective experience of line bisection in neglect. A re-analysis of their data can also offer insights into how best to characterise neglect performance for this and other tasks. We show that sensitive measures of neglect can be obtained by quantifying the difference in the influence (or 'weighting') that each endpoint has on the response. The right endpoint is dramatically more influential than the left in people with neglect performing line bisection and endpoint reproduction tasks. This supports the view that neglect may limit the ability to simultaneously represent two locations, so that the response is determined primarily with respect to the right endpoint. We also discuss Abe and Ishiai's conclusion that bisection responses in neglect are accompanied by the subjective experience of a complete line extending equally to either side of the chosen midpoint.

Peripheral reaching in Alzheimer's disease and mild cognitive impairment

Recent evidence has implicated areas within the posterior parietal cortex (PPC) as among the first to show pathophysiological changes in Alzheimer's disease (AD). Focal brain damage to the PPC can cause optic ataxia, a specific deficit in reaching to peripheral targets. The present study describes a novel investigation of peripheral reaching ability in AD and mild cognitive impairment (MCI), to assess whether this deficit is common among these patient groups. Individuals with a diagnosis of mild-to-moderate AD, or MCI, and healthy older adult controls were required to reach to targets presented in central vision or in peripheral vision using two reaching tasks; one in the lateral plane and another presented in radial depth. Pre-registered case–control comparisons identified 1/10 MCI and 3/17 AD patients with significant peripheral reaching deficits at the individual level, but group-level comparisons did not find significantly higher peripheral reaching error in either AD or MCI by comparison to controls. Exploratory analyses showed significantly increased reach duration in both AD and MCI groups relative to controls, accounted for by an extended Deceleration Time of the reach movement. These findings suggest that peripheral reaching deficits like those observed in optic ataxia are not a common feature of AD. However, we show that cognitive decline is associated with a generalised slowing of movement which may indicate a visuomotor deficit in reach planning or online guidance.

Did you see it? A Python tool for psychophysical assessment of the human blind spot

The blind spot is a region in the temporal monocular visual field in humans, which corresponds to a physiological scotoma within the nasal hemi-retina. This region has no photoreceptors, so is insensitive to visual stimulation. There is no corresponding perceptual scotoma because the visual stimulation is “filled-in” by the visual system. Investigations of visual perception in and around the blind spot allow us to investigate this filling-in process. However, because the location and size of the blind spot are individually variable, experimenters must first map the blind spot in every observer. We present an open-source tool, which runs in Psychopy software, to estimate the location and size of the blind spot psychophysically. The tool will ideally be used with an Eyelink eye-tracker (SR Research), but it can also run in standalone mode. Here, we explain the rationale for the tool and demonstrate its validity in normally-sighted observers. We develop a detailed map of the blind spot in one observer. Then, in a group of 12 observers, we propose a more efficient, pragmatic method to define a “safe zone” within the blind spot, for which the experimenter can be fully confident that visual stimuli will not be seen. Links are provided to this open-source tool and a user manual.

Attention attracts action in healthy participants: An insight into optic ataxia?

Patients with optic ataxia following lesions to superior parts of the posterior parietal cortex make large errors when reaching to targets in the peripheral visual field. These errors are characterised by a contraction, or attraction, towards the point of fixation. These patients also have a reduced ability to allocate visual attention away from the point of fixation, but it is unclear whether the core symptom of misreaching is related to these attentional problems. In neurologically-intact adults, we tested the effect of an attention-demanding dual-task performed at fixation upon visually-guided reaching to peripheral targets. The dual task was associated with delayed movement initiation, and a shortened deceleration phase of movement suggesting a reduced ability to benefit from online control. It also induced a small but consistent shift of reaching endpoints towards the side of fixation. Our experimental restriction of visual attention thus impaired both the programming and control of reaching, and induced a spatial pattern of errors that was qualitatively reminiscent of optic ataxia, albeit much less severe. These findings are consistent with a close functional link between attention and action in the healthy brain, and suggest that attentional disturbances could be a core component of optic ataxia following parietal lesions.

Power calculations in single-case neuropsychology: A practical primer

Researchers and clinicians in neuropsychology often compare individual patients against healthy control samples, to quantify evidence for cognitive-behavioural deficits and dissociations. Statistical methods for these comparisons have been developed that control Type I (false positive) errors effectively. However, remarkably little attention has been given to the power of these tests. In this practical primer, we describe, in minimally technical terms, the origins and limits of power for case-control comparisons. We argue that power calculations can play useful roles in single-case study design and interpretation, and we make suggestions for optimising power in practice. As well as providing figures, tables and tools for estimating the power of case-control comparisons, we hope to assist researchers in setting realistic expectations for what such tests can achieve in general.

The size-weight illusion in visual form agnosic patient DF

The size-weight illusion is a perceptual illusion where smaller objects are judged as heavier than equally weighted larger objects. A previous informal report suggests that visual form agnosic patient DF does not experience the size-weight illusion when vision is the only available cue to object size. We tested this experimentally, comparing the magnitudes of DF's visual, kinesthetic and visual-kinesthetic size-weight illusions to those of 28 similarly-aged controls. A modified t-test found that DF's visual size-weight illusion was significantly smaller than that of controls (z_cc = -1.7). A test of simple dissociation based on the Revised Standardized Difference Test found that the discrepancy between the magnitude of DF's visual and kinesthetic size-weight illusions was not significantly different from that of controls (z_dcc = -1.054), thereby failing to establish a dissociation between the visual and kinesthetic conditions. These results are consistent with previous suggestions that visual form agnosia, following ventral visual stream damage, is associated with an abnormally reduced size-weight illusion. The results, however, do not confirm that this reduction is specific to the use of visual size cues to predict object weight, rather than reflecting more general changes in the processing of object size cues or in the use of predictive strategies for lifting.

Assessment of visually guided reaching in prodromal Alzheimer's disease: a cross-sectional study protocol

INTRODUCTION

Recent evidence has implicated the precuneus of the medial parietal lobe as one of the first brain areas to show pathological changes in Alzheimer's disease (AD). Damage to the precuneus through focal brain injury is associated with impaired visually guided reaching, particularly for objects in peripheral vision. This raises the hypothesis that peripheral misreaching may be detectable in patients with prodromal AD. The aim of this study is to assess the frequency and severity of peripheral misreaching in patients with mild cognitive impairment (MCI) and AD.

METHODS AND ANALYSIS

Patients presenting with amnestic MCI, mild-to-moderate AD and healthy older-adult controls will be tested (target N=24 per group). Peripheral misreaching will be assessed using two set-ups: a tablet-based task of lateral reaching and motion-tracked radial reaching (in depth). There are two versions of each task, one where participants can look directly at targets (free reaching), another wheren they must maintain central fixation (peripheral reaching). All tasks will be conducted first on their dominant, and then their non-dominant side. For each combination of task and side, a Peripheral Misreaching Index (PMI) will be calculated as the increase in absolute reaching error between free and peripheral reaching. Each patient will be classified as showing peripheral misreaching if their PMI is significantly abnormal, by comparison to control performance, on either side of space. We will then test whether the frequency of peripheral misreaching exceeds the chance level in each patient group and compare the overall severity of misreaching between groups.

ETHICS AND DISSEMINATION

Ethical approval was provided by the National Health Service (NHS) East of England, Cambridge Central Research Ethics Committee (REC 19/EE/0170). The results of this study will be published in a peer-reviewed journal and presented at academic conferences.

Over- and underestimation of motor ability after a stroke: Implications for anosognosia

We administered a discrepancy-based measure of anosognosia for hemiplegia (AHP) to a group of 42 right-brain-damaged (RBD) and left-brain-damaged (LBD) stroke patients with varying levels of functional motor ability. In addition to the expected (anosognosic) pattern of overestimation of motor function in some RBD patients, we found an equal and opposite underestimation in some others, both RBD and LBD. We also found that around a quarter of self-estimation error could be predicted directly from actual ability, such that patients with poorer motor function tended to overestimate, and vice versa. This pattern suggests that some misestimation is attributable simply to statistical regression. However, even after adjusting for this regression effect, levels of overestimation were significantly greater in RBD patients, while LBD patients were more likely to underestimate their motor ability.

Grasping at laws: Speed-accuracy trade-offs in manual prehension

Most of human performance is subject to speed-accuracy trade-offs. For spatially constrained aiming, the trade-off is often said to take the specific form of Fitts' law, in which movement duration is predicted from a single factor combining target distance and target size. However, efforts to extend this law to the three-dimensional context of reaching to grasp (prehension) have had limited success. We suggest that there are potentially confounding influences in standard grasping, and we introduce a novel task to regularize the direction of approach and to eliminate the influences of nearby surfaces. In six participants, we examined speed-accuracy trade-offs for prehension, manipulating the depth (in the plane of the reach), height (orthogonal to the reach), and width (the grasped dimension) of the target object independently. We obtained lawful relationships that were consistent at the group and individual levels. It took longer to reach for more distant objects, and more time was allowed when placing the fingers on a contact surface smaller in either depth or height. More time was taken to grasp wider objects, but only beyond a critical width that varied between individuals. These speed-accuracy trade-offs showed substantial departures from Fitts' law, and were well described by a two-factor model in which reach distance and object size have separate influences on movement duration. We discuss empirical and theoretical reasons for preferring a two-factor model, and we propose that this may represent the most general form of speed-accuracy trade-off, not only for grasping but also for other spatially constrained aiming tasks. (PsycINFO Database Record

Developmental mirror-writing is paralleled by orientation recognition errors

The writing attempts of children often feature mirror-reversals of individual letters. These reversals are thought to arise from an adaptive tendency to mirror-generalize. However, it is unclear whether mirror-writing is driven by mirror-generalisation of the visual letter forms, or of the actions for writing them. We report two studies of the relationship between mirror-writing and the ability to recognize whether a visually presented letter is in the correct orientation, amongst primary and preschool children learning to read and write in English. Children who produced more mirror-writing also made more orientation recognition errors, for uppercase (Study 1, n = 44) and lowercase letters (Study 2, n = 98), and these relationships remained significant when controlling for age. In both studies, the letters more often reversed in writing were also more prone to orientation recognition errors. Moreover, the rates of mirror-writing of different uppercase letters were closely similar between the dominant and non-dominant hands (Study 1). We also note that, in the recognition tasks, children were more likely to accept reversed letters as correct, than to reject correctly oriented letters, consistent with a tendency to mirror-generalize the visual letter forms. In every aspect, these results support a major role for visual representations in developmental mirror-writing.

Experimental confirmation of a character-facing bias in literacy development

When learning to write, children often mirror-reverse individual letters. For children learning to use the Latin alphabet, in a left-to-right writing culture, letters that appear to face left (such as J and Z) seem to be more prone to reversal than those that appear to face right (such as B and C). It has been proposed that, because most asymmetrical Latin letters face right, children statistically learn this general regularity and are subsequently biased to write any letter rightward. The evidence for this character-facing bias is circumstantial, however, because letter-facing direction is confounded with other factors that could affect error rates; for instance, J and Z are left-facing, but they are also infrequent. We report the first controlled experimental test of the character-facing bias. We taught 43 Scottish primary schoolchildren (aged 4.8-5.8 years) four artificial, letter-like characters, two of which were left-facing and two of which were right-facing. The characters were novel and so were not subject to prior exposure effects, and alternate groups of children were assigned to identical but mirror-reflected character sets. Children were three times more likely to mirror-write a novel character they had learned in a left-facing format than to mirror-write one they had learned in a right-facing format. This provides the first experimental confirmation of the character-facing bias in literacy development and suggests that implicit knowledge acquired from exposure to written language is readily generalized to novel letter-like forms.

Attention and sensation in functional motor disorder

Functional motor disorder (FMD), also called psychogenic motor disorder or conversion disorder, describes impairments of motor function where there is no evidence of organic disease. The diagnosis is usually confirmed by positive clinical signs, such as Hoover's sign, in which normal power returns when attention is diverted away from the affected limb. This suggests that selective attention is an important determinant of these functional symptoms. The present study is the first specifically to explore the shifting of spatial attention in relation to the side of FMD. We tested 14 patients with unilateral functional upper limb weakness on three tasks requiring detection of visual targets close to the affected or unaffected hand, or touches to the hand itself. Targets were preceded by central cues promoting voluntary shifts of attention, or peripheral cues promoting automatic shifts. We observed a reduced response to visual and/or tactile targets on the affected side in around half of the patients, by comparison with age-matched controls, indicating that some degree of detection cost often accompanies FMD. Additionally, although the patient group showed normal cueing effects on the visual tasks, they had a unilateral absence of cueing effect on the affected side in the tactile task. Consideration of the data in the context of recent theory suggests that the abnormality may be not in the shifting of attention itself, but rather in the consequences of attending to the affected side. Specifically, the expected cueing effects may be absent on the affected side, because attention to a functionally weak limb increases the perception of the symptom, including any reduced sensory response. This preliminary research suggests promising new lines of investigation into the role of attention, and particularly somatic attention, in FMD.

Weight and see: Line bisection in neglect reliably measures the allocation of attention, but not the perception of length

Line bisection has long been a routine test for unilateral neglect, along with a range of tests requiring cancellation, copying or drawing. However, several studies have reported that line bisection, as classically administered, correlates relatively poorly with the other tests of neglect, to the extent that some authors have questioned its status as a valid test of neglect. In this article, we re-examine this issue, employing a novel method for administering and analysing line bisection proposed by McIntosh et al. (2005). We report that the measure of attentional bias yielded by this new method (EWB) correlates significantly more highly with cancellation, copying and drawing measures than the classical line bisection error measure in a sample of 50 right-brain damaged patients. Furthermore when EWB was combined with a second measure that emerges from the new analysis (EWS), even higher correlations were obtained. A Principal Components Analysis found that EWB loaded highly on a major factor representing neglect asymmetry, while EWS loaded on a second factor which we propose may measure overall attentional investment. Finally, we found that tests of horizontal length and size perception were related poorly to other measures of neglect in our group. We conclude that this novel approach to interpreting line bisection behaviour provides a promising way forward for understanding the nature of neglect.

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We used novel measures of attentional allocation to study line bisection behaviour in 50 right-brain damaged patients.

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These measures were more sensitive to neglect than was directional bisection error, and they correlated more highly with other core tests of neglect.

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We propose that one measure (EWB) reflects a lateral bias of attention, and the other measure (EWS) reflects overall attention.

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Perceptual biases on size-matching and landmark tasks did not correlate highly with line bisection, or any other core tests of neglect.

Saccade Reorienting Is Facilitated by Pausing the Oculomotor Program

As we look around the world, selecting our targets, competing events may occur at other locations. Depending on current goals, the viewer must decide whether to look at new events or to ignore them. Two experimental paradigms formalize these response options: double-step saccades and saccadic inhibition. In the first, the viewer must reorient to a newly appearing target; in the second, they must ignore it. Until now, the relationship between reorienting and inhibition has been unexplored. In three experiments, we found saccadic inhibition ∼100 msec after a new target onset, regardless of the task instruction. Moreover, if this automatic inhibition is boosted by an irrelevant flash, reorienting is facilitated, suggesting that saccadic inhibition plays a crucial role in visual behavior, as a bottom-up brake that buys the time needed for decisional processes to act. Saccadic inhibition may be a ubiquitous pause signal that provides the flexibility for voluntary behavior to emerge.

The end of the line: Antagonistic attentional weightings in unilateral neglect

The line bisection task is widely used in the study of neglect. Some years ago, McIntosh, Schindler, Birchall, & Milner (2005) proposed a radical reframing of this ubiquitous task. Rather than using the traditional measure of directional bisection error, they quantified the sensitivities of the response to the changing locations of the left and right endpoints of the line, expressing these as 'endpoint weightings'. A novel prediction generated from their analysis was that manipulations increasing attention to the left end of the line should cause an increase in the left endpoint weighting and a corresponding reduction in the right endpoint weighting. The present study fulfilled this prediction, using a forced-report cueing method in a group of 12 patients with left neglect. The data confirm an antagonistic relationship between endpoint weightings, consistent with the idea that they represent the sharing of a finite resource. It is argued that the endpoint weightings model of line bisection offers a sensitive and uniquely useful framework for studying competitive lateral biases of attention in neglect, and may also provide insight into non-lateralised attentional impairments.

Beyond the point of no return: effects of visual distractors on saccade amplitude and velocity

Visual transients, such as a bright flash, reduce the proportion of saccades executed, ∼60-125 ms after flash onset, a phenomenon known as saccadic inhibition (SI). Across three experiments, we apply a similar time-course analysis to the amplitudes and velocities of saccades. Alongside the expected reduction of saccade frequency in the key time period, we report two perturbations of the "main sequence": one before and one after the period of SI. First, saccades launched between 30 and 70 ms, following the flash, were hypometric, with peak speed exceeding that expected for a saccade of similar amplitude. This finding was in contrast to the common idea that saccades have passed a "point of no return," ∼60 ms before launching, escaping interference from distractors. The early hypometric saccades observed were not a consequence of spatial averaging between target and distractor locations, as they were found not only following a localized central flash (experiment 1) but also following a spatially generalized flash (experiment 2). Second, across experiments, saccades launched at 110 ms postflash, toward the end of SI, had normal amplitude but a peak speed higher than expected for that amplitude, suggesting increased collicular excitation at the time of launching. Overall, the results show that saccades that escape inhibition following a visual transient are not necessarily unaffected but instead, can reveal interference in spatial and kinematic measures.

Viewing Exemplars of Melanomas and Benign Mimics of Melanoma Modestly Improves Diagnostic Skills in Comparison with the ABCD Method and Other Image-based Methods for Lay Identification of Melanoma

Using an experimental task in which lay persons were asked to distinguish between 30 images of melanomas and common mimics of melanoma, we compared various training strategies including the ABC(D) method, use of images of both melanomas and mimics of melanoma, and alternative methods of choosing training image exemplars. Based on a sample size of 976 persons, and an online experimental task, we show that all the positive training approaches increased diagnostic sensitivity when compared with no training, but only the simultaneous use of melanoma and benign exemplars, as chosen by experts, increased specificity and diagnostic accuracy. The ABCD method and use of melanoma exemplar images chosen by laypersons decreased specificity in comparison with the control. The method of choosing exemplar images is important. The levels of change in performance are however very modest, with an increase in accuracy between control and best-performing strategy of only 9%.

Audio-visual integration and saccadic inhibition

Saccades operate a continuous selection between competing targets at different locations. This competition has been mostly investigated in the visual context, and it is well known that a visual distractor can interfere with a saccade toward a visual target. Here, we investigated whether multimodal, audio-visual targets confer stronger resilience against visual distraction. Saccades to audio-visual targets had shorter latencies than saccades to unisensory stimuli. This facilitation exceeded the level that could be explained by simple probability summation, indicating that multisensory integration had occurred. The magnitude of inhibition induced by a visual distractor was comparable for saccades to unisensory and multisensory targets, but the duration of the inhibition was shorter for multimodal targets. We conclude that multisensory integration can allow a saccade plan to be reestablished more rapidly following saccadic inhibition.

Transient involuntary mirror writing triggered by anxiety

Mirror writing (MW) has mainly been observed in left-hemisphere-damaged patients writing with the left hand. This study evaluated the presence of MW in 24 patients with mild cognitive impairment (MCI). We found that MW is not a typical feature of MCI. However, one woman (FC), mislabeled initially with MCI but in fact affected by anxiety, showed florid MW when writing with her left hand, which resolved as her anxiety receded. This case study supports anecdotal reports of MW triggered by anxiety, and the features of FC's performance indicate a motor rather than a perceptual basis for the phenomenon.

Look where you're going! Perceptual attention constrains the online guidance of action

Action guidance, like perceptual discrimination, requires selective attention. Perception is enhanced at the target of a reaching movement, but it is not known whether selecting an object for perception reciprocally prioritises it for action. Two theoretical frameworks, the premotor theory and the Visual Attention Model, predict that this reciprocal relation should hold. We tested the influence of perceptual attention on the online control of reaching. In Experiment 1, participants attended covertly to a flanker on one or other side of a fixated target, prior to reaching for that target, which occasionally jumped, after reach onset, to the attended or non-attended side. Participants corrected their reaches for almost all target jumps. In Experiment 2, we required covert monitoring of the flanker during reaching. This concurrent perceptual task globally reduced correction behaviour, indicating that perception and action share a common attentional resource. Corrections were especially unlikely toward the attended side. This is explained by assuming that perceptual attention primed an action toward the attended location and that the participant inhibited this primed action. The data thus imply that perceptual selection constrains online action guidance, as predicted by the premotor theory and the VAM. We further argue that the fact that participants can inhibit a location within the action system but simultaneously maintain its prioritisation for perceptual monitoring, is easier to reconcile with the VAM than with the premotor theory.

Distance-mediated spatial neglect

Unilateral spatial neglect (USN) is usually assessed by means of individual stimuli or single arrays of stimuli. Seldom are stimuli presented as multiple objects or in spatially separated blocks, except in some tests for object-based neglect. The distance between individual objects or blocks of stimuli in such stimuli is implicitly considered irrelevant. We report on the case of a patient, EC, who showed severe USN in his everyday behavior, yet performed normally on standard tests for USN. Presented with stimuli in separate blocks, he performed flawlessly with 4 cm gaps between blocks, yet ignored all leftward blocks of stimuli when the gap was larger than this. EC's dissociation between good performance on standard tasks and severe neglect with separate groups of stimuli, and the distance-mediated nature of his USN are novel observations with relevant theoretical and clinical implications.

Saccadic inhibition can cause the remote distractor effect, but the remote distractor effect may not be a useful concept

We have suggested that the remote distractor effect (RDE), the elevation of average saccadic reaction time (SRT) induced by a task-irrelevant distractor, may be explained as a statistical consequence of a characteristic reshaping of the SRT distribution known as saccadic inhibition (SI; Buonocore & McIntosh, 2008). In a recent paper, Walker and Benson (2013) argue against this idea and claim that the RDE and SI are partly dissociable. Here, we examine this claim, taking the opportunity to clarify potential ambiguities about how SI affects average SRT, and how the presence of SI can be inferred from SRT distributions.We highlight what we consider to be the most interesting aspects of Walker and Benson’s data, and suggest that a more flexible and nuanced view of SI can account for them. In considering the relation between SI and the RDE, we conclude that the RDE may no longer be a useful concept for eye movement researchers.

Image training, using random images of melanoma, performs as well as the ABC(D) criteria in enabling novices to distinguish between melanoma and mimics of melanoma

Robust experimental evidence supporting many attempts to facilitate early melanoma diagnosis is lacking. In an experimental study using a browser interface we have examined diagnostic accuracy, sensitivity and specificity of novices in distinguishing between melanomas and mimics of melanoma. We show that rule-based ABC methods and image training, based on random images of melanoma, improve specificity to similar degrees, with-out effects on sensitivity, leading to small improvements in overall accuracy. There was a significant effect of age with older subjects performing better. Although both the ABC method and image training groups showed improved performance over the control group, overall performance was poor. For instance, for a task in which 1 in 4 test images was a melanoma, and 3 out of 4 benign, both interventions (ABC or image training) increased accuracy from the control value of 53% to around 61%. For reference, dermatology trainees performed at a much higher level of accuracy. Our study provides little support for the use of such methods in public education, but suggests ways in which performance might be improved.

Mirror man: a case of skilled deliberate mirror writing

Mirror writing is a striking behaviour that is common in children and can reemerge in adults following brain damage. Skilled deliberate mirror writing has also been reported, but only anecdotally. We provide the first quantitative study of skilled deliberate mirror writing. K.B. can write forward or backward, vertically upright or inverted, with the hands acting alone or simultaneously. K.B. is predominantly left handed, but writes habitually with his right hand. Of his writing formats, his left hand mirror writing is by far the most similar in style to his normal handwriting. When writing bimanually, he performs better when his two hands make mirror-symmetrical movements to write opposite scripts than if they move in the same direction to write similar scripts. He has no special facility for reading mirrored text. These features are consistent with prior anecdotal cases and support a motor basis for K.B.'s ability, according to which his skilled mirror writing results from the left hand execution of a low-level motor program for a right hand abductive writing action. Our methods offer a novel framework for investigating the sharing of motor representations across effectors.

Phantabulation: a case of visual imagery interference on visual perception

We report the case of a 52-year old man who, following rupture of an anterior communicating artery aneurysm, presented with a phenomenon not previously described, which we have labelled "Phantabulation." Phantabulation is characterized by frequent and purposeful interactions with contextually appropriate imagined objects. We suggest that this phenomenon results from confusion between real and imagined objects, caused by failure to inhibit florid visual imagery, facilitated by cortical release mechanisms.

Retrieval practice, with or without mind mapping, boosts fact learning in primary school children

Retrieval practice is a method of study in which testing is incorporated into the learning process. This method is known to facilitate recall for facts in adults and in secondary-school-age children, but existing studies in younger children are somewhat limited in their practical applicability. In two studies of primary school-age children of 8-12 years, we tested retrieval practice along with another study technique, mind mapping, which is more widely-used, but less well-evidenced. Children studied novel geographical facts, with or without retrieval practice and with or without mind mapping, in a crossed-factorial between-subjects design. In Experiment 1, children in the retrieval practice condition recalled significantly more facts four days later. In Experiment 2, this benefit was replicated at one and five weeks in a different, larger sample of schoolchildren. No consistent effects of mind mapping were observed. These results underline the effectiveness of retrieval practice for fact learning in young children.

Visual and Proprioceptive Cue Weighting in Children with Developmental Coordination Disorder, Autism Spectrum Disorder and Typical Development

Accurate movement of the body and the perception of the body's position in space usually rely on both visual and proprioceptive cues. These cues are weighted differently depending on task, visual conditions and neurological factors. Children with Developmental Coordination Disorder (DCD) and often also children with Autism Spectrum Disorder (ASD) have movement deficits, and there is evidence that cue weightings may differ between these groups. It is often reported that ASD is linked to an increased reliance on proprioceptive information at the expense of visual information (Haswell et al, 2009; Gepner et al, 1995). The inverse appears to be true for DCD (Wann et al, 1998; Biancotto et al, 2011). I will report experiments comparing, for the first time, relative weightings of visual and proprioceptive information in children aged 8-14 with ASD, DCD and typical development. Children completed the Movement Assessment Battery for Children (MABC-II) to assess motor ability and a visual-proprioceptive matching task to assess relative cue weighting. Results from the movement battery provided evidence for movement deficits in ASD similar to those in DCD. Cue weightings in the matching task did not differentiate the clinical groups, however those children with ASD with relatively spared movement skills tended to weight visual cues less heavily than those with DCD-like movement deficits. These findings will be discussed with reference to previous DSM-IV diagnostic criteria and also relevant revisions in the DSM-V.

Attention modulates saccadic inhibition magnitude

Visual transient events during ongoing eye movement tasks inhibit saccades within a precise temporal window, spanning from around 60-120 ms after the event, having maximum effect at around 90 ms. It is not yet clear to what extent this saccadic inhibition phenomenon can be modulated by attention. We studied the saccadic inhibition induced by a bright flash above or below fixation, during the preparation of a saccade to a lateralized target, under two attentional manipulations. Experiment 1 demonstrated that exogenous precueing of a distractor's location reduced saccadic inhibition, consistent with inhibition of return. Experiment 2 manipulated the relative likelihood that a distractor would be presented above or below fixation. Saccadic inhibition magnitude was relatively reduced for distractors at the more likely location, implying that observers can endogenously suppress interference from specific locations within an oculomotor map. We discuss the implications of these results for models of saccade target selection in the superior colliculus.

Modulation of saccadic inhibition by distractor size and location

Distractors presented contralateral to a visual target inhibit the generation of saccades within a precise temporal window (Buonocore & McIntosh, 2008; Reingold & Stampe, 2002; Walker, Kentridge, & Findlay, 1995). The greatest 'dip' of saccadic inhibition typically occurs at about 90 ms after distractor onset, with a subsequent recovery period showing an elevated frequency of saccades. It is not yet known how the spatial properties of the distractor stimulus influence the saccadic inhibition signature. To study this, we manipulated the size and the field of presentation of the distractor in four experiments. Experiment 1 demonstrated that the size of a distractor in the contralateral field is logarithmically related to the magnitude of the saccadic inhibition dip. This implies that the probability of a planned saccade being inhibited increases logarithmically with the size of the distractor. Experiment 2 showed a qualitatively similar but more pronounced effect of size for distractors in the ipsilateral field. Experiment 3 compared the effects of contralateral and ipsilateral distractors directly using a within-subjects design, confirming the more pronounced impact of ipsilateral distractors. Experiment 4 replicated the more pronounced effect of ipsilateral distractors in a task in which target side was unpredictable, confirming that the effect does not result merely from participants preparing in advance to ignore events on one side. We suggest that participants are more able to resist contralateral distraction during target selection, as they can more effectively withdraw attention from locations remote from the target than from locations close to it.